1. Field of the Invention
The present invention relates to a disk spacer for a hard disk drive, and, more particularly, to a disk spacer for a hard disk drive having an improved shape so that vibration of a rotating disk can be reduced.
2. Description of the Related Art
Hard disk drives (HDDs) are one of many types of auxiliary memory devices of a computer which read data stored on a magnetic disk or record data on the magnetic disk by a magnetic head. To achieve high speed, high capacity, and low vibration of a hard disk drive, a variety of research and development is being performed.
FIG. 1 is an exploded perspective view illustrating a conventional hard disk drive. FIG. 2 is a vertical sectional view of the hard disk drive of FIG. 1.
Referring to FIGS. 1 and 2, a conventional hard disk drive includes a housing 10, a spindle motor 30 installed in the housing 10 to rotate a magnetic disk (a hard disk) 20, and an actuator 40 having a magnetic head (not shown) to record and reproduce data with respect to the disk 20.
The housing 10 is installed in a main body (not shown) of a computer and includes a base plate 11 supporting the spindle motor 30 and the actuator 40, and a cover plate 12 coupled to an upper portion of the base plate 11 to encompass and protect the disk 20.
The actuator 40 can pivot around a pivot shaft 47 installed on the base plate 11 by a voice coil motor 48. The actuator 40 includes an arm 46 coupled to the pivot shaft 47 to be capable of pivoting, and a suspension 44 installed at the arm 46 and supporting a slider 42 where the magnetic head is mounted to be elastically biased toward a surface of the disk 20.
One or a plurality of disks can be installed as a recording medium (media) for recording of data to be spaced apart by a predetermined distance and rotated by the spindle motor 30.
The spindle motor 30 is supported by a flange 31 fixedly installed on the base plate 11. An upper end portion of a shaft 32 of the spindle motor 30 is typically coupled to the cover plate 12 by a screw 36 and is fixed thereto. A bearing 37 is provided at the outer circumference of the shaft 32 so that a hub 33 can rotate. The disk 20 is inserted around the outer circumference of the hub 33. When a plurality of disks are installed, a ring type spacer 50 is installed around the outer circumference of the hub 33 to maintain a gap between the disks. A clamp 60 to prevent escape of the disk 20 is coupled to an upper end portion of the hub 33. Although the spacer 50 is typically used to maintain a gap between the disks, when only a single disk is installed, the spacer 50 may be used to fill a space between the disk 20 and the clamp 60.
FIG. 3 is a magnified perspective view illustrating a portion of the hard disk drive. FIG. 4 is a side view illustrating a slider that is shown in FIG. 3.
Referring to FIG. 3, a parking zone 21, where the slider 42 of the actuator 40 is parked when power is turned off, is provided at the inner circumferential side of the disk 20. A data zone 22, where magnetic signals are recorded, is provided outside the parking zone 21. In the data zone 22, servo signals indicating position of information to be recorded are recorded in advance on several tens of thousands of tracks formed along the circumference of the disk 20.
While the power of the hard disk drive is being turned off, the slider 42 is parked in the parking zone 21 of the disk 20 by an elastic force of the suspension 44. When the power is turned on and the disk 20 begins to rotate, lift is generated by air pressure and accordingly the slider 42 is lifted. The slider 42 in a lifted state is moved toward the data zone 22 of the disk 20 as the actuator 40 pivots. The slider 42 moved into the data zone 22 maintains a lifted state, as shown in FIG. 4, at a height where the lift by the rotation of the disk 20 and the elastic force of the suspension 44 are balanced. A magnetic head 41 mounted on the slider 42 maintains a predetermined distance from the disk 20 that is rotating and performs recording and reproduction of data.
However, in the conventional hard disk drive having the above structure, fluttering is generated in the disk 20 that is rotating by a variety of factors, in particular, by irregular movements of air inside the hard disk drive. FIG. 5 shows the flow of air formed around the disk 20 in a conventional hard disk drive which is commonly known. As shown in the drawing, the flow of air at the central portion of the disk 20 has the same direction (arrow B) as the rotation direction of the disk 20 (arrow A). A plurality of torrents (arrow C) are formed at the outer circumferential side of the disk 20. The torrents deter smooth flow of air around the disk 20. Accordingly, a local difference in temperature exists at the outer circumferential side of the disk 20. That is, the temperature of air at the portion where the torrents are generated is higher than at the other portions because the flow of air is not smooth. Such a deviation of temperature at the outer circumferential side of the disk 20 causes deviation in air pressure. As a result, the air pressure applied to the outer circumferential side of the disk 20 differs locally so that fluttering is generated in the disk 20.
In the disk fluttering, there is an RRO (repeatable runout), a component that is repeated at each rotation, and an NRRO (non-repeatable runout), a component that is not repeated. Since RRO is regularly repeated, it can be compensated by a servo control system. However, it is difficult to compensate NRRO because it cannot be anticipated in advance. The disk fluttering increases a PES (position error signal) so that data recording and reproduction capability of the magnetic head 41 is lowered. Thus, performance of a hard disk drive is deteriorated.
In particular, as the rotation speed of the disk 20 increases and the thickness of the disk 20 decreases, the disk fluttering increases further so that accurate data recording or reproduction is difficult with only the servo control system. Furthermore, as TPI (track per inch) increases, the disk fluttering makes accurate position control of the magnetic head 41 more difficult.
In light of the above, to secure reliability of performance of a hard disk drive, the disk fluttering generated during the operation needs to be lowered. Furthermore, with the recent trends toward high speed, high capacity, and low noise, lowering the disk fluttering is one of the most imminent issues to be solved.